"Educated estimate" is not idiomatic. Don't use it. "Educated guess" is idiomatic. An "educated guess" means exactly what it says. It's just a guess. It probably didn't involve numbers or calculations. But it is a guess made by someone who knows something about the topic. An "estimate" suggests something more precise and formal than a guess, and probably involves some kind of numbers or calculation. A "rough estimate" means an estimate that is not intended to be precise. A "ballpark estimate" is even less precise, and comes from an idiomatic saying, "it's in the ballpark" meaning it's not precise but it's somewhere in the same general area as the correct number. I'll add two more: a "back-of-the-envelope calculation" means an actual calculation made using remembered data, found numbers, and simplified assumptions. Literally, it means a calculation so simple you can scribble it out on a small piece of scrap paper. Here is one that is informal, and not quite polite because the word "ass" isn't polite: a "wild-assed guess." Occasionally people will use the acronym "WAG" to avoid saying the word "ass!" It means a guess that's even less precise than an "educated guess." "How long does it take to drive from Boston to Albany?" "No idea, I don't do it, but a wild-assed guess might be you could do the round-trip in a day with time to do something in Albany." "I do it all the time, and I can make an educated guess. I'd say two-and-a-half hours, but watch out for the congestion around the Worcester exit during the rush hour." "At a rough estimate, two-and-a-half to three hours." "We can do a back-of-the-envelope calculation. The distance is 170 miles, and the speed limit varies from 55 to 65 mph. If we make a ballpark estimate of 60 mph for speed, that would be 170 minutes... two hours, fifty minutes."

I have never heard the expression "educated estimate",but also "according to educated guess"guess" would be wrong. Being able to read the whole sentence would be helpful.